Raised pavement markers are commonly used as highway traffic markings that provide road lane delineation. The raised markers allow drivers of oncoming vehicles to correctly position themselves on the roadway, particularly at night or under conditions of poor visibility. Raised markers have the advantage of providing enhanced visibility, particularly when they incorporate retroreflective materials, and of also providing an audible signal to the driver when their automobile strays beyond the delineated area.
Raised pavement markers have been adhered to pavement surfaces using an asphalt or an epoxy type adhesive. Both of these adhesive systems, however, have certain drawbacks. For example, the bituminous asphalt type adhesive is cumbersome to apply and exposes workers to dangers involved with hot asphalt. The epoxy resin type adhesives require precise mixing and careful application of the materials and therefore can also be inefficient to provide adequate care for bond making.
Pressure-sensitive adhesives (PSAs) have been used in some pavement marking applications. PSAs, for example, have been used with durable pavement marking tapes and other such products (see e.g. U.S. patent application Ser. No. 08/760,356, filed Dec. 4, 1996). While there have been attempts to use PSAs for adhesion of raised pavement markers to roadway surfaces, these attempts have not been completely successful. Temporary raised pavement markers that are generally made of elastomeric or rubbery materials have been adhered to roadway surfaces for periods of about 3 to 6 months. For such markers, the adhesive pad is generally placed on one surface of the “L” shaped marker. When the marker is hit by a tire, the elastomeric material collapses and then bounces back up when the vehicle has passed. These markers are generally used in construction work areas where long term adhesion is not required. Examples of this type of marker are disclosed in U.S. Pat. No. 4,521,129, U.S. Pat. No. 4,534,673, U.S. Pat. No. 5,460,115 and U.S. Pat. No. 4,626,127.
Attempts to use a butyl rubber type adhesive for adhering durable raised pavement markers to road surfaces have encountered difficulties. One successful application has been where durable markers are used for special marking purposes. Normally, this special use marker is placed in the middle of the road where it does not get hit by vehicles. If a durable raised pavement marker could be adhered to a road surface for long periods of time using a pressure-sensitive adhesive, it would provide great advantages in convenience, safety, and efficiency of application.